Lifan 125cc Sputters and runs without power..

[Pitsterpits]

Hello, just joined this site!

I got a 125cc lifan engine with about 15 hours on it, that started sputter and run bad a few days ago..
I can't find out what it is, it idles great, no problem at all. In all gears it will sputter and run really bad, with no bottom end power at all! Runs like crap all of a sudden...

I've changed the air filter, inspected the outside of the carb all the way to the motor, no air leaks either. Tried to see if there's something not right with the wiring harness but everything seems alright...

Today, when I fired it up, it started with no problem at all, ran without problems for 15 minutes. then I turned it off and fired it back up, suddenly a lot of sputtering and ****. Then, I tried to ride it just to see, sometimes the sputter and powerloss would dissapear and come back...it's very weird.

Could this be carb that got crap in it?
Something wrong with the CDI, or coil?
Valves out of adjustment? I've never checked them.
Water in the fuel tank?, poored in new fresh fuel today, a few litres so it should be alright..

Thanks for any answers, hope to get this solved out pretty quick!

 

[stoozo]

Hello, just joined this site!

I got a 125cc lifan engine with about 15 hours on it, that started sputter and run bad a few days ago..
I can't find out what it is, it idles great, no problem at all. In all gears it will sputter and run really bad, with no bottom end power at all! Runs like crap all of a sudden...

I've changed the air filter, inspected the outside of the carb all the way to the motor, no air leaks either. Tried to see if there's something not right with the wiring harness but everything seems alright...

Today, when I fired it up, it started with no problem at all, ran without problems for 15 minutes. then I turned it off and fired it back up, suddenly a lot of sputtering and ****. Then, I tried to ride it just to see, sometimes the sputter and powerloss would dissapear and come back...it's very weird.

Could this be carb that got crap in it?
Something wrong with the CDI, or coil?
Valves out of adjustment? I've never checked them.
Water in the fuel tank?, poored in new fresh fuel today, a few litres so it should be alright..

Thanks for any answers, hope to get this solved out pretty quick!

When was the last time you changed the plug? If it was a china ngk its possibly on the way out after 15 hours....could be the carby. What kind of bike is it, what motor, what carby? Possibly could be a dodgy earth somewhere too, not sure about that one 100% though.

 

[my67xr]

welcome to Miniriders,

the valves would need adjusting for sure, do that as a starting point.

[video=youtube;QJciyJRJh8Q]http://www.youtube.com/watch?v=QJciyJRJh8Q[/video]

i would be taking the carby off and apart, give it a decent blow through with compressed air, so both the Main and Pilot jets, and the needle jet (what the main jet screws into)
the mixture screw, and the ports on the air filter side of the carby.
make sure all to holes are clear/open
when you have the main and needle jet out, look into the base of the carby where they screw into as well, check down the holes for any signs of dirt/corrosion.
when you refit the idle mixture screw, set it at about 1.5 turns out, then adjust it from there

take a photo of anything you are not sure of and post it up here.


also don't forget to drop by into out Introduce Yourself thread and say g'day too

cheers, craig

 

[Pitsterpits]

Thanks for some good replies

To start with, it is an Orion PRO 125, with the lifan 125cc engine, 2013 model. I bought it new!
I've always had fresh gasoline in it, so I wouldnt believe the carb to be clogged or anything...and it runs fine for some time and then turns weak and sputters...suddenly runs good again!
I've washed the pit bike pretty often, because when the snow melts here the roads turns a little nasty, I keep it clean, always changed the oil often, I mean really often. So it should be in good shape!
The first thing I changed out on it was the chineese spark plug, replaced it with a NGK! The plug colour looks good, light brown! And it always fires up quickly as well! I've set the carb to the best setting as well, dunno how many turns on the fuel screw though, but it ran very good until this sputter/bad power dilemma became an issue..
Perhaps it would be nice to put on a new 26mm Mikuni carb or something? Im not sure what the stock is...
I've also ordered a better CDI and coil already, heard the stock ones aren't especially good

This Pit bike is just used as a Trail Bike, I've got a YFZ 450 08', and a Predator 500 03' as well, but neighbours aren't that happy about them I guess, so the pit bike comes in useful when I just wanna take a ride

I will check into the valves, It seems real easy to do, and shouldnt take long!

 

[Pitsterpits]

What would be a good Carb to replace the stock with?

Im thinkin a MIKUNI VM22 26mm carb.. As long as it fits onto this engine

 

[gottagetacheaperhobby]

oko 24mm for the win there mate. easy to tune, more power and cheap

 

[my67xr]

what carby is on it now?
the OKO 24mm would be good for the track once you have jetted/tuned it, you will need an adapter, air filter and throttle cable to use it on your bike- NEW OKO 24mm Flatslide Race Carby KIT 140cc 150cc 160cc | eBay

or the Mikuni copy 22/26mm is a good all rounder, they run sweet on a 125 with a #20 Pilot(slow) Jet fitted to them
but are a little harder to tune due to the mixture screw being underneath at the front
NEW Mikuni 26mm Racing Carburetor KIT 140cc 125cc Lifan | eBay
NEW Mikuni Carburetor Slow Main Jets | eBay

 

[gottagetacheaperhobby]

^thats my problem with the mikunis, just to hard to tune.

 

[Pitsterpits]

Thats too bad! But Im used to carbs that a little hard to tune! Had my YFZ 450 jetted, been in and out of that carb a lot! it's a keihin, I guess they are pretty similar to Mikuni carbs...

Anyways, will look into carbs later, because today I decided to check the valves, my god it's easy! Found out that they were both too tight, I mean I couldnt get anything between them I shimmed them both up, intake to 0,05mm, and exhaust to 0,06mm, it fired right up afterwards! Ran like a champ
BUT, the manual says 0,10mm for both the intake valve and the exhaust valve, even though I've red many places that 0,06 and 0,05 is better.
Maybe it's just me, but I think the valves are ticking more now as well...would that be of concern? It runs flawless, idles great and has much more bottom end/ responsivnes to it!

 

[stoozo]

Thats too bad! But Im used to carbs that a little hard to tune! Had my YFZ 450 jetted, been in and out of that carb a lot! it's a keihin, I guess they are pretty similar to Mikuni carbs...

Anyways, will look into carbs later, because today I decided to check the valves, my god it's easy! Found out that they were both too tight, I mean I couldnt get anything between them I shimmed them both up, intake to 0,05mm, and exhaust to 0,06mm, it fired right up afterwards! Ran like a champ
BUT, the manual says 0,10mm for both the intake valve and the exhaust valve, even though I've red many places that 0,06 and 0,05 is better.
Maybe it's just me, but I think the valves are ticking more now as well...would that be of concern? It runs flawless, idles great and has much more bottom end/ responsivnes to it!

I'm pretty sure its supposed to be .003" inlet .004" exhaust

 

[Pitsterpits]

I will try that for sure why does the manual say 0.10? shouldnt all 125cc stock engines have the same clearance?

 

[stoozo]

I will try that for sure why does the manual say 0.10? shouldnt all 125cc stock engines have the same clearance?

Chinese pit bikes? Nah if its a 125 chinese engine pretty sure thats correct! .10 sounds like a mistake...thats why you've been getting tappet sound!

 

[Pitsterpits]

I have no clue what the valve clearance were from factory, but it has never made any ticking noise. The manual state 0.10mm actually, I've never adjusted the valves to those specifications!
I will go down to 003 on inlet and 004 on exhaust then, thanks for the info! Hopefully it will run even better

 

[my67xr]

.003 thou inlet (= .08mm), .004 thou exhaust (= .1mm)

it wouldn't have been ticking because the valves didn't have any clearance
as the engine warms up, the clearance gets smaller
if there was no clearance before you adjusted them, when i got warm, the valves wouldn't have been closing fully.
you would have burnt out your valves, and it would run like crap too

 

[Pitsterpits]

Are you talking about Millimeters or Inches?

It seems like you're talking about 004 inches, and thats about 0.10 millimeters! So the manual is right after all, I sat both the valves a little tight then, gonna change that right away! seemed to be running fine though!

 

[stoozo]

.003 thou inlet (= .08mm), .004 thou exhaust (= .1mm)

it wouldn't have been ticking because the valves didn't have any clearance
as the engine warms up, the clearance gets smaller

Ah yeah that makes sense....mine say .003/.076mm and .004/.102mm thats what I get for spending $15 on them

 

[Pitsterpits]

Yes yes, good to hear!
I didnt run it much when it ran bad, so the valves should be okey! Gonna make the clearance right, now! Their just a bit tight

 

[my67xr]

stu, that is the exact conversions you wrote,
most cheap feeler gauges don't have a lot of choices in between .07mm, and .08mm
the .002mm or .004mm extra clearance is not worth worrying about

 

[Pitsterpits]

Made the Valve clearance completely right now, haha! Well thats good It runs very good now, but still...would the valve ticking be of concern..it's a bit louder then normal In my opinion...But im not used to Pit bike engines so..

 

[my67xr]

as it warms up the clearances become smaller, so the ticking will fade out a bit.
it is a lot better for the engines' life

same thing happens as the valves beds in, and wear, the clearances get smaller, that is why you need to check them every 15 hours or so.
you can pick up a cheap hour meter and fit that to your frame if you want.
the black wire wraps around your spark plug lead and turns it on when the bike starts.
Hour Meter FOR Dirt Quad Bike ATV Motorcycle Snowmobile | eBay